Perpendicular magnetic recording (PMR) is approaching the maximum areal density (AD) that can be achieved with multi-layer media in which the magnetic anisotropy field (Hk) is graded from a low value in the top layer to a high value in the lowest layer. Therefore alternate recording technologies such as heat assisted magnetic recording (HAMR), which may encompass or be synonymous with additional technologies such as energy assisted magnetic recording (EAMR), are being investigated to achieve higher areal density.
HAMR technologies are intended to address the areal density problem. In these assisted recording systems, a laser beam is delivered through an optical waveguide and interacts with a near field transducer (NFT) that absorbs part of the optical energy and forms a very strong localized electromagnetic field in the near field region. When the localized electromagnetic field is close enough to the recording medium, the recording medium absorbs part of the localized electromagnetic field energy and is thereby heated up thermally, which helps to realize the magnetic recording process.
Recent atomistic calculations associated with HAMR media switching have revealed a relatively severe fast cooling rate problem for HAMR media. More specifically, for the fast cooling rates needed to support HAMR in high speed applications, theoretical results have revealed that conventional HAMR media experience fluctuations in magnetization and anisotropy during fast cooling which will cause grains to flip when they should not and to not flip when they should. This will lead to wide and noisy transitions with poor bit error rate performance. In addition, this will lead to DC-like noise proximate to the transitions but not at them, which is due to the associated magnetization and anisotropy fluctuations. As such, an improved magnetic media for use in HAMR applications that addresses these problems is desirable.